Interconnect for Ic Package

This application is a divisional of U.S. patent application Ser. No. 17/536,999 filed Nov. 29, 2021, which is incorporated herein by reference in its entirety.

This description relates to an interconnect for an integrated circuit (IC) package.

An interconnect (alternatively referred to as a lead frame) is a metal structure inside an integrated circuit (IC) package that carries signals from a die of the IC package to external components. An interconnect includes a central die pad, where the die is placed, surrounded by pads situated on a periphery of the interconnect.

Interconnects are manufactured by removing material from a flat plate of copper, copper-alloy, an iron nickel alloy, etc. To form the IC package, a die is adhered to the die pad of the interconnect. Also, wire bonds are attached between the die and pads of the interconnect to connect the die to the pads. In a process referred to as encapsulation, a plastic case is molded around the lead frame and die, exposing only the pads. The pads are cut off outside the plastic body and any exposed supporting structures are cut away.

A first example relates to an integrated circuit (IC) package that includes an interconnect with patches of unoxidized metal that are circumscribed by a region of roughened metal formed of oxidized metal. The IC package also includes a die mounted on the interconnect. The die is conductively coupled to at least a subset of the patches of unoxidized metal.

A second example relates to a method for forming an IC package. The method includes selectively etching a resist overlaying a sheet of interconnects to provide a mask of resist on the sheet of interconnects. The method also includes roughing, in response to the selectively etching, the sheet of interconnects. The method includes removing a remaining portion of the resist to provide the sheet of interconnects with units that have a smoothed portion and a roughened portion. The smoothed portion of the units has spaced apart patches of unoxidized metal, and the roughened portion has oxidized metal that circumscribed the patches of unoxidized metal.

This description relates to IC packages and methods for forming the IC packages. The IC packages include an interconnect that has a smoothed portion (unoxidized metal, such as unoxidized copper) and a roughened portion (oxidized metal, such as oxidized copper). More particularly, the interconnect includes spaced apart patches of unoxidized metal (part of the smoothed portion) that are circumscribed by a roughened region formed of oxidized metal (part of the roughened portion).

In some examples, the die is attached to the interconnect with a flip chip process. In such examples, the die includes posts extending from a surface of the die to contact the spaced apart patches of unoxidized metal on the interconnect. The spaced apart patches of unoxidized metal on the interconnect allow for improved solder wetting to securely mount the die on the interconnect. In complementary fashion, the roughened region of the interconnect that circumscribes the spaced apart patches of unoxidized metal impedes the flow of solder, thereby preventing solder bridges between posts of the die.

In other examples, the die is mounted on the interconnect with wire bonding. In such examples, the interconnect includes a die pad at a center of the interconnect, and pads at a periphery of the interconnect. In these examples, a first surface of the die is mountable on the die pad. The die is adhered to the die pad with an epoxy to electrically insulate the die from the die pad. Also, wire bonds are adhered to a second surface of the die, and to patches of the pads of the interconnect. The wire bonds are adhered to the patches of unoxidized metal on the pads of the interconnect with solder, and the patches of unoxidized metal provide improved solder wetting. In complementary fashion, the roughened region of the interconnect that circumscribes the spaced apart patches of unoxidized metal impedes the flow of solder, thereby preventing solder bridges between wire bonds.

Additionally, a molding (e.g., a mold compound) encases the interconnect and the die to provide the IC package, such as a quad flat no leads (QFN) IC package or a dual flat no leads (DFN) IC package. The portion of roughened metal (e.g., oxidized copper) on the interconnect provides improved purchase (e.g., grip) for the molding, such that the molding is securely adhered to the interconnect. The patches of unoxidized metal (forming the portion of smoothed metal) provide improved solder wetting compared to a region of roughened metal. Complementarily, the roughened portion formed of oxidized metal impedes the flow of solder and provides improved adherence to the molding relative to the smoothed region. Accordingly, by providing the interconnect with both the smoothed portion (e.g., unoxidized metal) and the roughened portion (e.g., oxidized metal), the benefits of an interconnect formed with either unoxidized metal or roughened metal are provided without the corresponding hindrances.

illustrates a cross-sectional view of an integrated circuit (IC) package. The IC packageincludes a diemounted on an interconnect(e.g., a lead frame). In the example illustrated, the dieis mounted on the interconnectusing flip chip techniques to form a QFN or a DFN package. The interconnecthas a smoothed portion of metal (e.g., unoxidized copper) and a roughened portion of metal (e.g., oxidized metal, such as oxidized copper). In particular, the interconnectincludes a central regionthat has a surfacethat has a region of roughened metal(oxidized metal) that is interrupted by spaced apart patches of unoxidized metal. That is, the spaced apart patches of unoxidized metal, which are a component of the smoothed portion of the interconnectare circumscribed by the region of roughened metal(e.g., oxidized metal), which is a component of the roughened portion of the metal. Stated differently, the smoothed portion of the interconnectincludes the spaced apart patches of unoxidized metalthat are circumscribed by part of the roughened portion of the interconnect, namely the region of roughened metalof the central region.

The dieincludes poststhat extend from a surfaceof the dieto the spaced apart patches of unoxidized metalon the central regionof the interconnect. The postsare adhered to the spaced apart patches of unoxidized metalwith solder(e.g., a solder ball or a solder paste). The region of roughened metalcircumscribes the spaced apart patches of unoxidized metal. Thus, the region of roughened metalforms a continuous surface on the central regionof the interconnect, such that a point of the region of roughened metalof the surfaceof the central regionis connected to another point on the central regionthrough a path (linear or curved) without crossing one of the spaced apart patches of unoxidized metal.

illustrates an overhead viewof the interconnectof, wherein the dieis removed. Thus, for purposes of simplification of explanation,employ the same reference numbers to denote the same structures. The interconnectincludes extensionsthat extend from the central regionof the interconnect to a pad (hidden from view) of a first type arranged on a periphery of the interconnect. The interconnectalso includes padsof a second type arranged around a periphery of the interconnect. The padsof the second type include a patch of unoxidized metalthat is circumscribed by a remaining portion of roughened metal(e.g., oxidized metal). That is, the padsof the second type include a first portion of unoxidized metal, namely, the patch of unoxidized metal, and a second (remaining) portion of oxidized metal, namely the region of roughened metal. Thus, the patch of unoxidized metalon the padsof the second type is part of the smoothed portion of the interconnect. Similarly, the region of roughened metalon the padsof the second type is part of the roughened portion of the interconnect. Conversely, the padsof the first type have a surface that is covered completely (or nearly completely) with roughened metal (hidden from view in).

In the example illustrated, there are six (6) spaced apart patches of unoxidized metalon the central regionof the interconnect, only some of which are labeled. In other examples, there are more or less spaced apart patches of unoxidized metal. Additionally, there are four (4) padsof the first type and eight (8) padsof the second type, only some of which are labeled. In various examples, there are more or less padsof the first type and more or less padsof the second type. The spaced apart patches of unoxidized metalare circumscribed by the region of roughened metalof the central region. Additionally, as illustrated in the overhead view, the padsof the second type are arranged at the periphery of the interconnect. The padsof the second type include the patch of unoxidized metalcircumscribed by the region of roughened metal. Conversely, the padsof the first type include a region of roughened metaland do not include a patch of unoxidized metal.

Referring back to, the spaced apart patches of unoxidized metalat the central regionof the interconnectenable excellent solder wetting. Similarly, patches of unoxidized metalon the padsof the second type also enable excellent solder wetting. Accordingly, the spaced apart patches of unoxidized metaland the patches of unoxidized metalenable the poststo be securely adhered to the spaced apart patches of unoxidized metalof the central regionof the interconnectand to the padsof the second type. Accordingly, the dieis electrically coupled to the set of unoxidized metal patches, namely, the spaced patches of unoxidized metalon the central regionand the patches of unoxidized metalon the padsof the second type. In complementary fashion, the region of roughened metalon the central regionof the interconnect provides a barrier for the solderto prevent solder bridging between postsof the die.

The interconnectand the dieare encased in a molding. The moldingis formed of a molding compound, such as plastic or similar material. Also, the region of roughened metalon the central region, the region of roughened metalon the padsof the second type and the roughened metalon the padsof the first type improve adherence of the moldingto the interconnect.

By employment of the interconnect, the benefits of roughing portions (oxidizing metal) of the interconnectare attained without drawbacks. More particularly, because the interconnectincludes the spaced apart patches of unoxidized metal(components of the smoothed portion) on the central regionand the padsof the second type include the patches of unoxidized metal, the dieis securely mounted on the interconnectto enable robust electrical communication between the dieand the padsof the first type and the padsof the second type. More specifically, the smoothed patches of unoxidized metal allow for excellent solder wetting. Complementarily, the interconnectalso includes the region of roughened metalat the padsof the second type (circumscribing the patches of unoxidized metal), the region of roughened metalof the central region(circumscribing the spaced apart patches of unoxidized metal) as well as the roughened metalon the padsof the first type. These regions of oxidize metal forming the region of roughened metalof the central regionand the regions of roughened metalon the padsof the second type impede the flow of solder, thereby preventing solder bridges. Stated differently, the regions of oxidize metal forming the region of roughened metalon the central region of the interconnectprovides a barrier to prevent solder adhering to a given postto the central regionor a padof the second type from bridging to another post. These regions of roughened metal, such as the region of roughened metal, the roughened metalon the padsof the first type and roughened metalon the padsof the second type also improve purchase (e.g., grip) between the interconnectand the molding, thereby improving adherence between the moldingand the interconnect. Accordingly, providing the interconnectwith patches of unoxidized metal (e.g., smoothed copper) and regions of roughened metal (e.g., oxidized copper), provides the benefits of an interconnect formed with an unoxidized metal and an interconnect formed with an unoxidized metal without the respective drawbacks.

illustrates a cross-sectional view of another example IC package. The IC packageincludes a diemounted on an interconnect(e.g., a lead frame) with wire bonding to form a QFN or DFN package. More particularly, the dieis mounted on a die padof the interconnect. The interconnecthas a smoothed portion of metal (e.g., unoxidized copper) and a roughened portion of metal (e.g., oxidized metal, such as oxidized copper). In particular, the die padhas a surfacethat has a region of roughened metal(oxidized metal) that is interrupted by a patch of unoxidized metal. That is, the patch of unoxidized metal, which is a component of the smoothed portion of the interconnectis circumscribed by the region of roughened metal(e.g., oxidized metal), which is a component of the roughened portion of the metal. Stated differently, the smoothed portion of the interconnectincludes the patch of unoxidized metalthat is circumscribed by part of the roughened portion of the interconnect, namely the region of roughened metalof the die pad.

A first surfaceof the dieis mounted on the patch of unoxidized metalwith a layer of epoxy(e.g., an industrial glue) to adhere the dieto the die padand to provide electrical isolation between the first surfaceof the dieand the die pad. That is, the first surfaceof the dieis adhered to the patch of unoxidized metalof the die padwith the epoxy. The region of roughened metalcircumscribes the patch of unoxidized metal. Thus, the region of roughened metalforms a continuous surface, such that a point of the region of roughened metalof the surfaceof the die padis connected to another point on the surfacethrough a path (linear or curved) without crossing the patch of unoxidized metal.

The interconnectalso includes padsarranged around a periphery of the interconnect. The padsinclude a patch of unoxidized metalthat is circumscribed by a remaining portion of roughened metal(e.g., oxidized metal). That is, the padsinclude a first portion of unoxidized metal, namely, the patch of unoxidized metal, and a second (remaining) portion of oxidized metal, namely the region of roughened metal. Thus, the patch of unoxidized metalon the padsis part of the smoothed portion of the interconnect. Similarly, the region of roughened metalon the padsis part of the roughened portion of the interconnect.

illustrates an overhead viewof the interconnectof, wherein the dieis removed. Thus for purposes of simplification of explanation,employ the same reference numbers to denote the same structures. As illustrated, there are twelve (12) patches of unoxidized metalon the pads. In other examples, there are more or less padssuch that there are corresponding more or less patches of unoxidized metalon the pads. The patches of unoxidized metalare circumscribed by the region of roughened metalof the die pad. Additionally, as illustrated in the overhead view, the padsare arranged at the periphery of the interconnect. The padsinclude the patch of unoxidized metalcircumscribed by the region of roughened metal.

Referring back to, wire bondsare coupled to a second surfaceof the dieand to the patch of unoxidized metalon the padsthrough solder(e.g., a solder ball or solder paste). Accordingly, the dieis electrically coupled to the patches of unoxidized metal. The second surfaceof the dieopposes the first surfaceof the die. Because the dieis electrically insulated from the patch of unoxidized metal, the dieis electrically coupled to a subset of patches of unoxidized metal, namely the patches of unoxidized metal.

The patches of unoxidized metalof the die padenables excellent epoxy wetting. Accordingly, the patch of unoxidized metalallows the dieto be securely adhered to the die pad. Similarly, the patch of unoxidized metalon the padsenables excellent solder wetting to allow the solderto securely adhere to the pads. Additionally, the region of roughened metalcircumscribing the corresponding patch of unoxidized metalprevents the solder from bridging with another connection.

The interconnectand the dieare encased in a molding. The moldingis formed of a molding compound, such as plastic or similar material. The region of roughened metalon the padsand the region of roughened metalof the die padimprove adherence of the moldingto the interconnect.

By employment of the interconnect, the benefits of roughing portions (oxidizing metal) of the interconnectare attained without drawbacks. More particularly, because the die padincludes the patch of unoxidized metal(components of the smoothed portion) and the padsinclude the patches of unoxidized metal, the dieis securely mounted on the interconnectto enable robust electrical communication between the dieand the pads. More specifically, the smoothed patches of unoxidized metal allow for excellent solder wetting. Complementarily, the interconnectalso includes the region of roughened metalat the pads(circumscribing the patches of unoxidized metal) and the region of roughened metalof the die pad(circumscribing the patch of unoxidized metal). The regions of oxidize metal forming the region of roughened metalof the die padand the roughened metalof the padsprovides a barrier to prevent solder bridging between connections. These regions of roughened metal also improve purchase (e.g., grip) between the interconnectand the molding, thereby improving adherence between the moldingand the interconnect. Accordingly, providing the interconnectwith patches of unoxidized metal (e.g., smoothed copper) and regions of roughened metal (e.g., oxidized copper), provides the benefits of an interconnect formed with an unoxidized metal and an interconnect formed with an unoxidized metal without the respective drawbacks.

illustrate methods for forming interconnects for an IC package, such as the IC packageof. For purposes of simplification of explanation,employ the same reference numbers to denote the same structure.

In a first stage, as illustrated in, at, a sheet of interconnectsis provided. In some examples, the sheet of interconnectsis formed of copper (Cu). In other examples, other oxidizable metals are employable to form the sheet of interconnects. The sheet of interconnects include unitsthat are singulatable into individual interconnects, such as the interconnectof. These unitsinclude a central region, padsof a first type and padsof a second type arranged around a periphery of each respective unitin the sheet of interconnects. Only some of the padsof the first type and padsof the second type are labeled.

In a second stage, as illustrated in, at, the sheet of interconnectsis pretreated with industrial cleaning material to clean the sheet of interconnects. In a third stage, as illustrated in, at, a layer of resist(e.g., photoresist) is laminated (e.g., deposited) on the sheet of interconnects. In some examples, the layer of resistis a coating of polyimide overlaying a surface of the sheet of interconnects.

In a fourth stage, as illustrated inat, the resistis selectively etched to pattern the sheet of interconnectsto expose portions of the sheet of metal (e.g., bare copper). Stated differently, at, the resistis selectively etched to provide a mask of resiston the sheet of interconnects. More particularly, the resistis etched such that the resist (the resistof) covers portions of the sheet of interconnectsthat will form the central regionsand padsof the interconnects, and remaining portions (only some of which are labeled) of the sheet of interconnectsare exposed metal. Additionally, a regionof the resistis not etched to allow formation of a barcode on the sheet of interconnects.

In a fifth stage, as illustrated inat, the exposed portions of the sheet of interconnectsare roughened. More particularly, the remaining portion of the sheet of interconnectsthat is exposed (at operation) is oxidized to roughen a surface of the sheet of interconnects(formed of metal) to provide a portion of roughened metalof the sheet of interconnects. Additionally, the portions of the sheet of interconnectsunderlying the resistremain unoxidized (e.g., remain smooth). In a sixth stage, as illustrated in, at, the remaining portions of the resistare removed (e.g., in a wet etching process) to reveal a sheet of interconnectsthat each have a central regionand padsof the first type and padsof the second type. The sheet of interconnectsincludes patches of unoxidized metal, only some of which are labeled. The patches of unoxidized metalare employable to receive posts of a die on a central regionthat are circumscribed by a region of roughened metal(oxidized portion of metal). Further, at, a barcodeis inscribed (e.g., with a laser) on a patch of unoxidized metal corresponding to the regionof the resist of. In some examples, the barcodeis a two-dimensional barcode (e.g., a quick response (QR) code). In other examples, the barcodeis a one-dimensional barcode. The barcodeallows the sheet of interconnectsto be uniquely identified in a database. Further, by inscribing the barcodeon the patch of unoxidized metal, the readability of the barcodeis improved. Conversely, if a barcode were to be inscribed in the region of roughened metal, such a barcode would have an inconsistent surface (due to the roughing), which would make such a barcode difficult to read. Conversely, the barcodeis inscribed in unoxidized (smoothed) metal, enabling a scanner (or other device) to read the barcodewithout difficulty.

In a seventh stage, as illustrated in, at, the unitsin the sheet of interconnectsofare singulated to provide an array of interconnects. The singulation can be executed, for example, with a laser, a saw, bending, stretching, etc. The singulation separates the barcodefrom the array of interconnects. Each resultant interconnectincludes a central region, padsof the first type and padsof the second type. The central regionof the interconnectsand the padsof the second type include patches of unoxidized metalfor mounting posts. Additionally, the padsof the first type of the interconnectsare covered with roughened metal. Each interconnectis employable to implement the interconnectof.

illustrate methods for forming an IC package using flip chip techniques, such as the IC packageof. For purposes of simplification of explanation,employ the same reference numbers to denote the same structure.

In a first stage, as illustrated in, at, an interconnectis provided. In some examples, the interconnectis formed from the method of. The interconnectincludes a central regionsituated at a center of the interconnect. Also, the interconnectincludes pads(e.g., padsof the first type of) arranged at a periphery of the interconnect. The central regionincludes spaced apart patches of unoxidized metal(smoothed regions) that are circumscribed by a region of roughened metal(oxidized metal). Similarly, the padsinclude patches of unoxidized metalcircumscribed by regions of roughened metal.

In a second stage, as illustrated in, at, a dieis mounted on the interconnect. The dieincludes postsextending from a surfaceof the dieto a corresponding patch of unoxidized metal. The postsare mounted on the spaced apart patches of unoxidized metalwith solder, such as solder past or a solder ball. The region of roughened metalimpedes the flow of solder. Thus, the solderfor adhering each respective postto a corresponding patch of unoxidized metalis contained within or near the boundaries of the patch of unoxidized metal, such that solder bridges between postsare not inadvertently formed.

In a third stage, as illustrated in, at, a molding(e.g., a molding compound) encases the interconnectand the dieto form the IC package. The regions of roughened metalon the padsand the region of roughened metalon the central regionensure that the moldingis securely adhered to the interconnect. Accordingly, as described herein, providing the interconnectwith patches of unoxidized metal (e.g., smoothed copper) and regions of roughened metal (e.g., oxidized copper), provides the benefits of an interconnect formed of an oxidized metal and an interconnect formed of an unoxidized metal without the respective drawbacks.

illustrate another example method for forming interconnects for an IC package, such as the IC packageof. For purposes of simplification of explanation,employ the same reference numbers to denote the same structure.

In a first stage, as illustrated in, at, a sheet of interconnectsis provided. In some examples, the sheet of interconnectsis formed of copper (Cu). In other examples, other oxidizable metals are employable to form the sheet of interconnects. The sheet of interconnects include unitsthat are singulatable into individual interconnects, such as the interconnectof. These unitsinclude a die padand padsarranged around a periphery of each respective unitin the sheet of interconnects. Only some of the padsare labeled.

In a second stage, as illustrated in, at, the sheet of interconnectsis pretreated with industrial cleaning material to clean the sheet of interconnects. In a third stage, as illustrated in, at, a layer of resist(e.g., photoresist) is laminated (e.g., deposited) on the sheet of interconnects. In some examples, the layer of resistis a coating of polyimide overlaying a surface of the sheet of interconnects.

In a fourth stage, as illustrated inat, the resistis selectively etched to pattern the sheet of interconnectsto expose portions of the sheet of metal (e.g., bare copper). Stated differently, at, the resistis selectively etched to provide a mask of resiston the sheet of interconnects. More particularly, the resistis etched such that the resist (the resistof) covers portions of the sheet of interconnectsthat will form the die padsand padsof the interconnects, and remaining portions (only some of which are labeled) of the sheet of interconnectsare exposed metal. Additionally, a regionof the resistis not etched to allow formation of a barcode on the sheet of interconnects.

In a fifth stage, as illustrated inat, the exposed portions of the sheet of interconnectsare roughened. More particularly, the remaining portion of the sheet of interconnectsthat is exposed (at operation) is oxidized to roughen a surface of the sheet of interconnects(formed of metal) to provide a portion of roughened metalof the sheet of interconnects. Additionally, the portions of the sheet of interconnectsunderlying the resistremain unoxidized (e.g., remain smooth). In a sixth stage, as illustrated in, at, the remaining portions of the resistare removed (e.g., in a wet etching process) to reveal a sheet of interconnectsthat each have a die padand padsof the second type. The sheet of interconnectsincludes patches of unoxidized metal, only some of which are labeled. The patches of unoxidized metalon the die padare employable to mount a die, and the patches of unoxidized metalon the padsare employable for attaching a wire bond to couple the die and the pads. The patches of unoxidized metalare circumscribed by a region of roughened metal(oxidized portion of metal). Further, at, a barcodeis inscribed (e.g., with a laser) on a patch of unoxidized metal corresponding to the regionof the resist of. In some examples, the barcodeis a two-dimensional barcode (e.g., a QR code). In other examples, the barcodeis a one-dimensional barcode. The barcodeallows the sheet of interconnectsto be uniquely identified in a database. Further, by inscribing the barcodeon the patch of unoxidized material, the readability of the barcodeis improved. Conversely, if a barcode were to be inscribed in the region of roughened metal, such a barcode would have an inconsistent surface (due to the roughing), which would make such a barcode difficult to read. In contrast, the barcodeis inscribed in unoxidized (smoothed) metal, enabling a scanner (or other device) to read the barcodewithout difficulty.

In a seventh stage, as illustrated in, at, the unitsin the sheet of interconnectsofare singulated to provide an array of interconnects. The singulation can be executed, for example, with a laser, a saw, bending, stretching, etc. The singulation separates the barcodefrom the array of interconnects. Each resultant interconnectincludes a die padand pads. The die padof the interconnectsand the padsinclude patches of unoxidized metalfor mounting posts. Each interconnectis employable to implement the interconnectof.

illustrate methods for forming an IC package using wire bonding, such as the IC packageof. For purposes of simplification of explanation,employ the same reference numbers to denote the same structure.

In a first stage, as illustrated in, at, an interconnectis provided. In some examples, the interconnectis formed from the method of. The interconnectincludes a die padsituated at a center of the interconnect. Also, the interconnectincludes padsarranged at a periphery of the interconnect. The die padincludes a patch of unoxidized metal(smoothed regions) on a surfacethat is circumscribed by a region of roughened metal(oxidized metal). Similarly, the padsinclude patches of unoxidized metalcircumscribed by regions of roughened metal.

In a second stage, as illustrated in, at, a dieis mounted on the die padof the interconnect. More particularly, a first surfaceof the dieis mounted on the patch of unoxidized metalwith an epoxy. The region of roughened metalimpedes the flow of epoxy.

In a third stage, as illustrated inat, wire bondsare mounted on a second sideof the dieand on a respective pad. The wire bondsare mounted on the padswith solder(e.g., a solder ball or solder paste). The region of roughened metalon each padimpedes the flow of solder, such that the solderis contained within or near boundaries of the patch of unoxidized metal.

In a fourth stage, as illustrated in, at, a molding(e.g., a molding compound) encases the interconnectand the dieto form the IC package. The regions of roughened metalon the padsand the region of roughened metalon the die padensure that the moldingis securely adhered to the interconnect. Accordingly, as described herein, providing the interconnectwith patches of unoxidized metal (e.g., smoothed copper) and regions of roughened metal (e.g., oxidized copper), provides the benefits of an interconnect formed of an oxidized metal and an interconnect formed of an unoxidized metal without the respective drawbacks.

illustrates a flowchart of an example methodfor providing interconnects for forming IC packages, such as the IC packageofor the IC packageof. At, a sheet of interconnects (e.g., the sheet of interconnectsofor the sheet of interconnectsof) is provided. The sheet of interconnects includes units that are singulatable into individual interconnects. The sheet of interconnects is formed, for example, with copper. At, the sheet of interconnects is pretreated in a cleaning process.

At, a layer of resist (e.g., the resistof) is deposited on the sheet of interconnects, such that the resist overlays the sheet of interconnects. At, the resist is selectively etched to provide a mask on the sheet of interconnects, such as illustrated in. More specifically, the resist is etched such that patches (e.g., the patches of resistof) of the resist are circumscribed by exposed bare metal.

At, in response to the selectively etching, the sheet of interconnects are roughened such that the exposed bare metal is oxidized. Conversely, portions of the sheet of interconnects covered by the patches of resist remain unoxidized.

At, a remaining portion of the resist (e.g., the patches of resist) is removed to provide a sheet of interconnects comprising a units that have a smoothed portion of unoxidized metal and a roughened portion of metal. The smoothed portion of the units are spaced apart patches of unoxidized metal on a die pad and a patch of unoxidized metal on pads of the units. At, a barcode (e.g., the barcodeof) is inscribed (e.g., with a laser) in a particular patch of unoxidized metal.